1. Field of the Invention
The present invention is related to a medium position determining device in which a scanning carriage is configured to move in a reciprocating manner in a scanning direction, and a controller is configured to move the scanning carriage in the scanning direction at a first speed before the scanning carriage reaches a predetermined position, and at a second speed after the scanning carriage reaches the predetermined position.
2. Description of Related Art
Ink jet printers, such as serial printers, are known in the art. In the known ink jet printer, a recording head which introduces ink into an actuator and ejects the ink under pressure using either; the deflection of the actuator; such as a piezoelectric element, an electric strain element, or the like, or the local boiling of the ink due to a heat generating element in response to an input signal, is mounted on a scanning carriage. The scanning carriage moves in a reciprocating manner in a direction that is orthogonal to the conveying direction of a recording paper, and the scanning carriage performs scamming each time the recording paper is conveyed at a predetermined linefeed width. The recording head ejects the ink based on the input signal, thus recording an image on the recording paper.
In such a known ink jet printer, to accurately align the position of the image with respect to the recording paper, left and right edge positions of the recording paper are detected. Specifically, when the image recording is performed to peripheries of left and right edges of the recording paper, that is, when marginless printing is performed, there is a need to accurately detect left and right edge positions of the recording paper.
The detection of edges of the recording paper is performed, for example, by mounting an optical sensor which includes a light, emitting portion which irradiates light to a recording medium, and a light receiving portion which receives a reflection light from the recording medium on a scanning carriage, by performing scanning while irradiating the light to a recording paper, and by detecting the presence of the recording paper in response to an amount of the reflection light.
Referring to FIG. 30, in the known ink jet printer, the detection of the edge of the recording paper is performed, before the image recording performed by the recording head, by activating the optical sensor 90 and by moving the scanning carriage 91 in the width direction of the recording paper P in the vicinity of a front edge of the recording paper P. An output signal of the optical sensor 90 is stored in a storing unit, such as a memory, by correlating the output signal with an encoder amount which indicates a position of the scanning carriage 91, and left and right edge positions of the recording paper P are detected based on the encoder amount of the scanning carriage 91 by analyzing the output signal.
Further, when the recording paper P is arranged obliquely, it is preferable to perform the edge detection of the recording paper P is performed, such that the edge detection of the recording paper P is performed not only in the vicinity of the front end of the recording paper P, but also for every predetermined conveying amount, as indicated by a chained line in FIG. 30. Then the image recording is performed based on obtained left and right edge positions. However, while accurate image recording may be realized by this edge detecting method, because edge detection is performed several times, the image recording speed is reduced.